Field of the Invention
The present invention relates to an image forming apparatus, a control method therefor, and a computer-readable storage medium storing a program for implementing the control method.
Description of the Related Art
In recent years, the time required to start an image forming apparatus has continued to increase. One of the causes is that the amount of data which should be expanded from ROM to RAM at start-up has been increasing with increase in functions of an image forming apparatus.
Accordingly, there has been a technique that, when a user turns off a power-supply switch, holds data as it is in RAM, and when the user turns on the power-supply switch the next time, skips expansion of data from ROM to RAM so as to shorten the time required for start-up.
Examples of this technique include a technique called suspend, which holds data in RAM by continuing to pass electric current through the RAM (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. H09-34578).
There has also been a technique called hibernation, which holds data in RAM by temporarily saving data in RAM to an HDD (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2000-82014).
According to these techniques, the time required for start-up can be shortened while it appears to a user that power to an image forming apparatus appears is off.
Further, recent image forming apparatuses provide power-supply control using software in response to user operation of a power-supply switch.
Conventionally, power is electrically turned off in response to operation of a power-supply switch, and hence in an image forming apparatus having a separation mechanism for a developing device and a photosensitive drum, the developing device and the photosensitive drum may be attached to each other when power is off (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2004-77692).
Accordingly, control is provided such that when power is to be turned on, the developing device attached to the photosensitive drum is separated from the photosensitive drum so as to check positions of the developing device and the photosensitive drum, and then the developing device is attached again to the photosensitive drum.
Thus, in an image forming apparatus that provides power-supply control using software in response to operation of a power-supply switch, a developing device and a photosensitive drum are separated from each other when power is to be turned off, so that a separation process can be skipped when power is turned on later, and the time required for start-up can be shortened.
In an image forming apparatus that provides power-supply control using software in response to operation of a power-supply switch, a measure is taken against a situation where software falls into an unexpected state due to a bug or the like (such as a state of being unable to leave a specific process). Specifically, the image forming apparatus has a timer power-off function of turning off power to at least a printer engine among hardware mechanisms when a predetermined time period has elapsed since a power-off operation was detected. This function ensures power-off in response to a power-off operation.
In a case where an image forming apparatus is configured to continue passing electric current through RAM even if a power-off operation is performed in order to shorten the time required for start-up of the image forming apparatus, it should appear to a user that power to the image forming apparatus is off even when electric current is being passed through RAM. In this case, the image forming apparatus lies in a high-speed start-up standby state in which power to at least a printer engine is turned off, and units in a controller other than RAM are placed in a power-saving state to the extent possible.
When a power-on operation is performed in this high-speed start-up standby state, it should appear to the user that this is the same as normal power-on. Accordingly, even when there is a print job prior to the high-speed start-up standby state, it is necessary to delete the print job and complete a start-up process with no print job present.
Aimed high-speed start-up cannot be realized by deleting, during a start-up process, a print job input prior to the high-speed start-up standby state, and hence in general, a print job is deleted before shifting into the high-speed start-up standby state.
A problem explained hereafter, however, will arise when an image forming apparatus is configured to exert the timer power-off function even when shifting into the high-speed start-up standup state while deleting a print job in accordance with a power-off operation. For example, as shown in FIG. 9, there may be cases where due to time-consuming deletion of a print job, a time-out occurs with some processing incomplete, and power to a printer engine is turned off, resulting in an engine protection command being too late.
In the case of a printer engine having a separation mechanism, it is necessary to, at the time of shifting into the high-speed start-up standby state, carry out a separation process before turning off power to the printer engine, but there may be cases where the separation process cannot be carried out due to the effect of a print job deletion process.
As a result, at the time of returning from this high-speed start-up standby state due to a power-on operation later, a separation process that is actually unneeded is carried out as a start-up process for a printer engine, and as shown in FIG. 9, an initialization process requires long time, slowing start-up.
On the other hand, when a set time for the timer power-off function is relatively long, the original purpose of taking a measure against a situation where software falls into an unexpected state due to a bug or the like cannot be accomplished.